The maximum data density that can be achieved by magnetic storage media is limited to 60-100 Gb/inch2 by the superparamagnetic limit. Alternatives to magnetic storage media are needed to further increase data density.
One such alternative developed by IBM Research is the “millipede” high-density data storage system. The millipede system is based on micromechanical structures taken from atomic force microscopy (AFM). Data is written as depressions in a polymer medium by a thermomechanical AFM probe. The data is also read and erased by the same probe. The millipede system includes an array of probes that operate in a highly parallel manner, so that each individual probe capable reads, writes and erases data in a small area. See, Vettiger et al., “The ‘Millipede’—More than one thousand tips for future AFM data storage,” IBM J. RES. DEVELOP., vol. 44, no. 3, pp. 323-339 (May 2000), which is incorporated herein by reference, for additional details regarding this technology.
This technology, however, has a number of drawbacks. Since the technology uses an indentation in the polymer medium to record data and a thermal conduction sensing scheme to read the data, it requires very good temperature control of the array and polymer medium between read and write cycles. Specifically, the temperature of the probe array chip must be maintained at 350° C. As a result, large energy consumption is expected due to heat loss. Also, the technology requires critical material selection with matching thermal expansion coefficients. Additionally, data bit size is limited to 40 nm by the size of the AFM probes as well as the indentation profile the probes create in the polymer media. Accordingly, data density, while increased over magnetic storage media, is limited to 500 Gb/inch2. Furthermore, read and write processes are slow, limited by the maximum resonant frequency of the cantilever probes, which are only operable on a microsecond scale.
Accordingly, a data storage device and system having increased data density is needed.